So you're saying that if you make a fortitude armor, you get all the bonuses listed.

Why are the bonuses split up like that between armor and weapon? Spirit is written in much the same way, but I'm pretty sure that it applies to either sword or shield, and the bonuses are different for each.

Runeword items have the standard abilities of the runes themself and bonus abilities. For weapons, the standard mods are different then the ones for armors, so look up e.g. here which mods are for weapons and which are for armors. For example, a Fortitude armor has +5 max lightning res from the Lo rune while that rune will provide a 20% chance for deadly strike for a weapon.